There is a growing interest in the enhancement of human potential by means of non-invasive brain neuromodulatory techniques. Transcranial direct current stimulation (tDCS) is a type of neuromodulatory technique that shows great promise as it is low cost, safe, well tolerated, clinically applicable and capable of inducing long-term behavioral after-effects. Placebo and nocebo effects are a critical component of clinical care and efficacy studies. Harnessing these effects by directly modulating the excitability of certain brain regions will have a significantly high impact on both medical practice and neuroscience. The goal of this proposal is to explore how excitability changes in the right dorsolateral prefrontal cortex (rDLPFC) induced by tDCS can modulate placebo analgesia and nocebo hyperalgesia in both healthy and patient populations. In Experiment 1, we will investigate the modulation effects of enhancing/inhibiting excitability of the rDLPFC on the neural circuitry underlying placebo / nocebo responses in a healthy population. In Experiment 2, we will focus on the neural mechanisms underlying the placebo effect in chronic low back pain (cLBP) patients by increasing the excitability of the rDLPFC. Furthermore, we will also explore whether boosted analgesic expectancy of heat pain can enhance clinical improvement in cLBP patients. The ability to enhance and inhibit excitability of specific brain regions in humans and investigate its effect on human behavior is key to understanding brain function and circuitry. Using devices such as tDCS allows us to move forward from observation to a more mechanistic understanding of neural causation. The results achieved in this study will shed new light on harnessing the self-control capacities to optimize the placebo and nocebo effects in clinical practice and research, facilitating development of new pain management methods, and elucidating the relationship between the human brain and behavior.